RFR: 8359701: G1: Move heap expansion time tracking of G1CollectedHeap:expand to call site

[Thomas Schatzl]

On Mon, 16 Jun 2025 15:35:59 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple patch of moving time-tracking logic from callee to caller, which removes a default arg. The default-arg is there because there are other callers that don't use/need this time-tracking logic.
> 
> Test: tier1

Marked as reviewed by tschatzl (Reviewer).

src/hotspot/share/gc/g1/g1CollectedHeap.cpp line 2395:

> 2393:     // No need for an ergo logging here,
> 2394:     // expansion_amount() does this when it returns a value > 0.
> 2395:     Ticks expand_start_instant = Ticks::now();

Suggestion:

    Ticks expand_start = Ticks::now();


It is very unusual to add an `_instant` postfix to similar variables, regardless of whether using `Ticks` or the `elapsedTime` API, so I suggested to remove it.

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PR Review: https://git.openjdk.org/jdk/pull/25835#pullrequestreview-2934248722
PR Review Comment: https://git.openjdk.org/jdk/pull/25835#discussion_r2151396041